Not since the arrival of the atomic clock has the Earth experienced such a short day as July 29.
In fact, it was a whopping 1.59 milliseconds faster than a standard 24-hour day.
But it’s no flash in the pan either – just three days earlier the Earth was spinning 1.50ms faster.
More than half of the world’s shortest days since 1970 were recorded in 2020.
These endless temporal changes may not seem particularly important (your boss might have poor eyesight if it was used as an excuse to be late for work), but they matter when it comes to accurate timekeeping around the world.
To ensure that the world remains in sync, a series of super-sophisticated atomic clocks are used to keep time to the nanosecond.
They do this by measuring vibrations in cesium atoms, which vibrate at a fairly rapid 9.2 billion times per second.
They are calibrated to be accurate to one second after 30 million years.
But while atomic clocks are very good at keeping accurate time, astronomical time is far less consistent, and as the world spins out of sync – due to fluctuations in rotation speed – they need to be corrected.
Leap seconds for a slower spin
The problem timekeepers have is that the Earth’s rotation is slowing down.
This is because the gravitational pull of the Moon and Sun stretches the Earth’s oceans, resulting in a loss of friction and a reduction in energy available for the planet to spin.
Because of this, the Earth spins around three milliseconds slower every century.
As the days are generally longer, Earth’s custodian of time and rotation—the International Earth Rotation and Reference Systems Service (IERS)—occasionally adds a “leap second” to keep clocks aligned with the planet’s rotation. So far, 27 jumps have occurred since 1972.
Why are we speeding up?
It’s accepted that days will get progressively longer over time, so the fact that record rotations have occurred recently has scientists scratching their heads.
Some suggest that interactions taking place below the Earth’s surface may have something to do with it.
Around the planet’s solid iron core is a layer of molten rock in motion. Our surface is constantly being crushed and pulled apart by the movement of tectonic plates.
Climate change has also been suggested as a possibility, as has the “Chandler oscillation” which refers to small, occasional changes in the way the Earth spins on its axis. Sometimes, because our planet is not a perfect sphere, it varies during rotation – think of how a top sometimes wobbles as it spins around.
Regardless of the cause of the Earth’s rapid spin, a negative a leap second may need to be considered to recalibrate global clocks in the future if this pace continues.
But not if Facebook and friends have anything to say about it…
Two engineers at Meta, Facebook’s parent company, say the impact of a negative leap second has never been tested on a large scale; it can have a devastating effect on software that relies on timers or schedulers.
Oleg Obleukhov and Ahmad Byagowi’s blog resumed the debate around how time unites.
Ten years ago, a leap second added to the world’s clocks affected Qantas flight check-ins, and some of the world’s largest websites and digital services.
On New Year’s Day 2017, Cloudflare—a huge internet security software provider—had a brief blackout when their software broke. As the company’s chief technology officer John Graham-Cumming explained, “a number was negative when at worst it should always be zero. A little later this negative value caused [the system] to panic.”
Obleukhov and Byagowi argue that “smearing”—a practice where a leap second is broken up and introduced over a longer period (Facebook spreads it over a 17-hour period starting at 00:00:00 UTC)—is a better way to handle these on. small time jumps.
Since 2008, Google has smeared time over 24 hours and also offers its own network time protocol that smears times to “smoothly handle leap seconds without disruptive events.”
Although some observers note that smearing is not a perfect solution to the inconsistent time problem, there is one option available to at least keep the internet running smoothly.